High indoor allergen and pollutant levels have repeatedly been linked to asthma morbidity, especially among urban children, who have among the highest asthma morbidity in the US. However, environmental intervention trials for asthma have typically compared an environmental control strategy (ECS) to no intervention, a design that does not reflect the recommended approach to asthma management, which includes ECSs in conjunction with titration of controller medication. As a result, it remains unknown whether the addition of an ECS to controller medication titration results in improved asthma control, and therefore a reduced controller medication requirement. Another unanswered question is whether the addition of an ECS to controller medication titration results in greater reduction of allergic inflammation than medication titration alone. ECSs may have a greater effect on allergic inflammation than controller medications because ECSs target the most upstream point of the asthma inflammatory pathway by reducing pro-inflammatory environmental exposures, while controller medications target a downstream point of this pathway. Surprisingly, it is also unknown whether the improvement in asthma in ECS trials is mediated by reductions in allergen levels and/or reduction in pollutant levels. Understanding the factors that mediate the effects of an ECS on asthma is important for refuting, or supporting, a causal role for indoor allergens and/or pollutants in asthma morbidity, and also for optimizing the design of ECSs to target the most influential factors. We therefore hypothesize that the addition of an individually-tailored, multi-faceted ECS to guidelines-based controller medication titration will result in less controlle medication requirement and allergic inflammation than controller medication titration alone among urban asthmatic children. We will test this hypothesis and identify the factors that mediate the clinical effects of the ECS with a parallel-arm, randomized controlled trial of ECS plus controller medication titration vs. controller medication titration alone. Our aims are: (1) T determine the effect of the addition of ECS to controller medication titration on controller medication requirements and allergic inflammatory biomarkers, and (2) To determine whether reductions in particulate matter (PM) and/or indoor allergens mediate the effects of an ECS on asthma. This proposed trial will answer a pivotal question because if ECSs do not provide additional benefit in the context of treatment with controller medication, the role of ECS in asthma management should be downgraded. On the other hand, if ECSs do indeed reduce controller medication requirements, greater emphasis should be placed on the importance of ECSs in asthma management, studies should be conducted to identify best ECS practices, and policies should be changed to require third party payers to cover ECS costs.